JPEG XL Image Loader for imlib2

This is a loader for imlib2 that adds support for reading and writing JPEG XL files. This lets you view them using feh, for example. It relies on libjxl for encoding and decoding the images.

All JPEG XL files are supported, with the following limitations:

• All images are internally converted to ARGB with 8 bits per sample, and transformed to an sRGB color profile - this is a limitation of imlib2.
• For animated JXLs, only the first frame is decoded.

You probably don't need this loader

imlib2 now comes with its own JXL loader, so you might prefer to use that.

• imlib2's loader can decode all frames of animated JXLs, while this one only decodes the first.
• imlib2's loader uses less memory.
• imlib2's loader is better behaved with respect to reporting progress and allowing decoding to be cancelled half way.

On the other hand,

• This loader ensures the pixels fed back to the library are using a standard sRGB profile, which gives more consistent results. imlib2's loader ignores color profiles.

Build / Install

The loader has been built and tested on Linux (Kubuntu x86_64, Arch x86_64) using gcc and clang.

Since imlib2 introduced its own JXL loader, installation of this alternative loader requires you to remove, rename or replace the official one, since imlib2 always prefers to use the loader named jxl.so before considering any others.

Dependencies

• imlib2 with development headers (libimlib2-dev for Debian and similar).
  • Specifically, the build requires Imlib2_Loader.h. On Arch, this is installed comes with the imlib2 package.
• libjxl with development headers.
• (Optional) liblcms2 with development headers (liblcms2-dev for Debian and similar).

Arch Linux

There is a PKGBUILD available in AUR for easy installation of the latest release on Arch Linux:

git clone https://aur.archlinux.org/imlib2-jxl.git
cd imlib2-jxl
# (You should now review PKGBUILD before proceeding)
makepkg -s
sudo pacman -U imlib2-jxl-x.y.z.pkg.tar.zst

Note, this AUR package rudely overwrites the jxl.so distributed with the imlib2 package!

To install the cutting-edge git version, use the alternative package from https://aur.archlinux.org/imlib2-jxl-git.git.

Other Linuxes

Ensure the above dependencies are installed. Download the imlib2-jxl source - either a release archive or the latest commit:

git clone https://github.com/alistair7/imlib2-jxl.git

Then simply running make should produce jxl.so:

cd imlib2-jxl
make
sudo make install

make install attempts to find the right location for the loader via pkg-config and copy jxl.so there. If this fails, you'll have to manually identify the directory for imlib2 loaders and copy jxl.so there yourself. On 64-bit Kubuntu this is /usr/lib/x86_64-linux-gnu/imlib2/loaders. On Arch this is /usr/lib/imlib2/loaders.

Note, make install overwrites the jxl.so distributed with the imlib2 package!

Debug Build

Use the debug target of the makefile to produce an unoptimized build that includes debugging symbols and prints information to stderr while it runs. The resulting library will be called jxl-dbg.so. Use install-debug to copy this to imlib2's loader directory.

make debug
sudo make install-debug

You must remove jxl.so in order for imlib2 to see jxl-dbg.so.

Building without lcms2

You can build this loader without lcms2 - this simply disables color management. This requires editing 3 lines in Makefile:

• Remove -DIMLIB2JXL_USE_LCMS from CPPFLAGS.
• Remove pkg-config lcms2 --cflags from SHARED_CFLAGS.
• Remove pkg-config lcms2 --libs from LDFLAGS.

feh

If you are using a version of feh between 3.6 and 3.7.0, inclusive, JXL files will not be recognised (due to #505), and you will get an error similar to

feh WARNING: asdf.jxl - Does not look like an image (magic bytes missing)

To avoid this, set FEH_SKIP_MAGIC=1 in feh's environment, and it will start working.

This workaround is no longer necessary since feh version 3.7.1, which recognises JXL's signature.

Copying

All source code in this repository is available under the BSD-3-Clause License, © Alistair Barrow